Spray metal coated



NOV. 30, 1943. J M N Re. 22,398 I SPRAY METAL COATED, METAL SURFACED ARTICLE Original Filed Aug. 6, 1942 Fig. 3

. Q INVENTORQ John Finn]: M

Reis'sued Nov. 30,

. SPRAY METAL COATED, METAL summon!) ARTICLE John Frank Meduna.

Seattle. Wash" assignor to Metallizing Engineering 00., Inc.,

Long Islan City, N. Y., a corporation of New Jersey Original No.

2,320,329,4lated May 25 1943, Serial No. 453,905, August 6, 1942.

Application for reissue Augustll, 1943, Serial No. 498,609

8 Claims- This invention relates to new and useful improvements in spray metal coated, metal-surfaced articles.

In industrial practice, a coating of metal is frequently applied metal by spraying. For this purpose, the metal to be applied is projected against the surface to be covered'in the form of a spray, the particles of which are in a molten or heat plastic condi-. tion. As a rule, metal spra'ylng is carried out with the use of metal spray guns, i.e., devices in which the metal is fed to a heating zone from which zone metal particles, at least some of which are molten min a heat plastic condition, are propelled against the surface to be sprayed,

by a blast of air or other gas. The application of sprayed metal may, for example, be carried out toprotect the base against corrosion, to provide a surface of the desired ornamental or bearing characteristics, or to build up worn machine parts.- p

In making spray metal coated articles, particularly re-built bearings or other working surfaces of machine parts, it is essential that the applied spray metal adheres to the surface to which it is applied with a high degree of bond,

for, otherwise the applied spray metal will come off. In the past, spray metal coated. metal-surto a base of the same or other relatively high faced articles have been generally of two kinds.

Those in which the base is pre-conditioned for spray metal bondingby mechanical roughening and those in which the baseis so pre-condition'ed by heating.

Mechanical roughening of a metal surface to adapt the same to receive and retain applied spray metal must mation of a multiple number of closely spaced cavities withpeened and splayed edges and interspaces, forming amultitude of keyways. Hitherto, the most common method of procuring such type surface has been by sand or grit blasting. Sand or grit blasting, however, is in many cases unsatisfactory and spray metal coated articles, obtained from such sandor grit blasted surfaces will often come part by reason of the deficient bond obtaining between the spray metal coating and the blasted surface. This is'particularly true when heavier spray metal coatings have been applied to substantially flat surfaces and in cases where spray metal has been applied to surfaces forming an inside diameter. metal has a tendency to shrink and in these ,cases the sand or grit blasted surface does not provide a suiiicient bonding surface to prevent the" separation of the applied spray metal coating Spray be of a type involving the formetal articles or surfaces from the base. For this reason, has never been practical to make spray metal coated, hardened engine valve seats or similar objects in which an especially strong bond between the spray metal coating andthe' base is required. Furthermore, many bases and particularly those constituted by machine tools or parts such as, for instance, generator shafts or the like, are inherently unsuitable for sand or grit blasting.

An alternative form of mechanical surfaceroughening for spray metal bonding purposes is that of machine toughening the surface to be sprayed in a. particular manner designed to procure the above-mentioned istics essential for spray metal bondin The articles obtained by this roughening method, 7

however, are subject to substantially the same inherent limitations and drawbacks as those prepared from a sand or grit blasted base.

The heating method of surface conditioning a metallic base to bond thereto applied spray metal involves the heating of the surface to a temperature and tospray the hot surface with metal. This method is not .widely used and requires, as a general rule, considerable skill and elaborate equipment and is relatively expensive. Furthermore, in most cases 'the temperature to which the surface or base must be heated is so high that it tends to warp or otherwise destroy the article to which the metal spray is to be applied. Hence, it is in many cases impossible to obtain satisfactory spray metal coated articles havin the spray metal directly heat bonded to its base.

There is one basic limitation inherent in practically all of the hitherto used spray metal bonding means. This limitation resides in the fact that those bonding means are not adaptable to hardened m- 1 articles or surfaces. Many hardened arti es or surfaces cannot be properly surface-conditioned by mechanical roughening procedures such as grit or sandblasting or rough-machining. 0n the other hand, the heating method is not feasible, for most such will soften and thus lose their hardness if they are heated to the temperature necessary to secure the desired degree of bonding to the spray metal applied thereto. Though partly hardened articles have been prepared by grit or sand blasting, usingv very hard grit such as aluminum oxide abrasives,

nevertheless,- the bond obtained is usually unsatisfactory. l

for instance, it

surface charactermetal coated, metal-surfaced articles.

. from. the following description.

whiehawlreorber.

One object of the invention comprises inter.

alia a spray metal coated, metal-surfaced article substantially free from the limitations and drawbacks characterizing hitherto known'spray 'I'hisand further objects of the invention will beapparent The spray metal coated, metal-surfaced article in accordance with the inventlon'essentially com prises an article havinga metal surface, a layer of spray metal, and; intermediate said metal surface upon and bonded to said surface by fusion and by an irregular surface frozen from seml-llquid state with a multitude of. projections with overhanging edges and minute craters with overhanging-edges, at least the majority of said 7 cases electrode siseand'electrlc current should be suitably coordinated. V i

Contact between the metal electrode and the metal surface to be conditioned for the metal spraying operationis established in the ordinary manner by placing the electrode indirect con- 1 and said layer of spray metal, metal deposited f projections and craters being in interlock with spray metal particles of said la r of spray metal. I have found that best results and a particularly good interlock with the superimposed spray metal are obtained byso selecting the sizeand spacing of the projections and craters on the.

surface of the fusion-deposited metal that the same are of substantially the same order of magnitude as the size of spray metal particles in the spray mctallayer.

Within the prefe rred embodiment of the invention the irfiegular surface of fusion-deposited metal is preferably so constituted as to have in addition to the projections of the order of mag nitude of spray metal particles, projections of a higher order of magnitude and preferably of an order of magnitude not appreciably in excess of 1 These projections of higher order of magnitude, though not necessarily-acting as interlocks with spray metal particles of the superim- ,sliwaseofthespraymetallayerwlthrespectto tact with such surface. Within the range of normal requirements, practically any metal sur-y face and any metal electrodemay be used. In case, however, any particular electrode metal should prove unsuitable or unsatisfactory in its application to a given metal surface of a base to be conditioned for spraying; the operator can determine by a few simple empirical tests as to which electrode metal to select. As a practical guide anytwo metals that can be joined by. heating will operate as electrode material on the sur-' face to be conditioned for spraying. The electric heating of the contacting surfaces of the metal electrode and metal surface to be conditioned for spraying may be efiected' by plac ing the electrode and the metal surface in, elecf heating I mean that the trio circuit with a source ofelectrical energy in such manner that the circuit is closed by contact between the metal troder The conditions of current flow in the cir-- cult upon so closing the same are preferably so adjusted that conditions of resistance heating at surfaces of electrode and metal surface maintain. By conditions of resistance current flowing through the contacting surfaces is in amount'and intensity sufficient to cause heating at the.v contacting surfaces by the resistance offered the free flow ofithe' current by reason of the jointconstituted bythe contacting surfaces posed layer of spray metal, nevertheless, contrib- 'ute to the bond by counteracting or preventing 'thebasesurfaceresultingfromtheshrinkageof the applied spray m One. method, inter alia, of preparing a spray metal coated article in accordance with the inyention may be forlnstance by the deposition of electrode material upon the metal surface of such article and thesubsequent application of spray metaltothethuslytreatedbase. procedure of depositing electrode material involves" establishing contact l'ntween such metal surface thatmaysbeusedis ofthewh'etrmiiesoftbctspoin mam! 36cahmexeiatnicheiwire coustitutesantround,"flat" or ofelectrodeis preferred.

Though voltages having a widen-nae, including relatively high voltages ,of the order of mag- .or two hlmdred volts or nitude of one hundred and the metal Ielec:

nickel wire electrode.

I of the electrode relative the metal base.

of relatively small or at least fairly sharp pointed electrodes so that the procedure is slow. In genbond will result. and therefore where a strong bond is not desired the deposits may be quite eral, a satisfactory current will depend upon the voltage, the size of the electrodes and principally upon the amount of contact between th electrode and the metal surface of the base to be The amount of current to be used may vary over a wide range depending upon the factors hereinabove recited. As a general rule, when using wire electrodes a current in excess of two hun dred amperes and most preferably a current of the order of magnitude of about 300 to 400 amperes is satisfactory. Thus, for instance, a 300 ampere current gives good results with a /8" When using larger electrodes the use of larger amounts of current may be necessary.

The deposition of small amounts of electrode material may be caused either by the melting off;

of small amounts of electrode material from the tip of the electrode or by pulling on small amounts of fused surface bonded electrode materialfrom'the tip of the electrode when moving the latter. In the majority of cases, deposition,

of electrode material may be caused in both of these manners. Moving of the electrode will as a rule, accomplish the desired deposition of small amounts of electrode material firmly bonded to the surface area to which electrode contact was applied.

The metal surface to be conditioned for spray above set forth, with a suitable metal electrode metal application when inserted in circuit, as

and a suitable source of electric energy is prefer- I ably repetitiously contacted'such as repetitiously contact stroked with the electrode on successive areas, .the stroking action depositing on these areas small amounts of electrode material firmly bonded thereto. Alternatively, the electrode may be applied with a stippling action to the metal surface. While these procedures essentially involve breaking and making contact' between the metal surface andthe-electrode, it is 'I also possible and sometimes .advisable to move the electrode relative the base while maintaining resistance-heating contact therebetween. When widely spaced. For 'a strong bond, however, it is preferred to have spaces between amounts of -metal spraying, the height of these larger type projections is preferably kept at less than the thickness of the spray metal coating to be applied, i. e., less than as", as otherwise, if the spray metal coating is machined smooth, these projections will extend through the coating to the machined surface. There are,- however, some applications where this is no disadvantage.

It is sometimes advantageous to make the larger type, projections relatively so high that they will xtendto beyond the thickness of the coating of, sprayed metal that is to be applied, and then, machine oil or tool off their tops, so that they will not project through the spray metal coating to be applied. Thereafter, the metal coat'may be applied.

If desired, small amounts of metal may be fu-. sion-deposited, as described previously, to the baseand thenthe deposition continued so that more metal is so deposited on top of metal previously deposited, as wel1 as in the spaces between previously fusion-deposited metal, a relatively thick metal may be "applied- Within normal requirements, the thickness of the coating of in vtermediate-layer metal has, in itself,as a rule, no effect upon the bond with which the subse-' quently applied spray metal is held thereto and thus to the base surface of the spray metal coatber of patterns. For instance, the metal may be proceeding in thisv manner, electrode material is.

depositedin ridges along the path ofmovement on the other hand, in themaking and breaking contact method small amounts of' individual electrode material are deposited upon the metal base. The procedure is continued or repeated in either case until the surface to be sprayed is satisfactorily covered with electrode material. Care should be taken that the electrode is not left in a contact position too long at any one point or area as this may cause the permanent attachment of the electrode to the base andthus render its further movement and further deposit of electrode material impossible.

It is not necessary to have'everyspot on the metal base covered by the fusion-deposited metal; on the contrary of metal with spaces in between some of them.- The size of the spaces between deposited amounts of metal may be varied over a reasonably wide range at the judgment of the operator. Broadly stated, the smaller the spaces the stronger a deposited, although in small successive amounts, in strips or ridges, or it may be deposited in separate isolated spots, or, for instange, in crisscross pattern.

The following examples are furnished by way of illustrating procedures for procuring my novel spray metal-coated metal-surfaced articles:

Example I A source of electric energy consisting of a.

J transformer connected to an alternating current power supply is first provided, capable of an average voltage between two and nine volts and approximately 300 amperes. One lead from the source of electric energy 'is connected to Va A" steel plate, the top surface of which is to receive fusion-deposited metal and has been suitably cleaned such as by application of (2014 to remove grease and dirt. The other ladfrom the source of electrical energy is connected to a nickel wire of approximately diameter. The nickel wire is first contacted with'the top surface of the steel plate and as soon as the metal of the electrode starts to meltthe contacted surface is lightly and continuously stroked with the nickel wire over successive areas of-the same whereby the end of the nickel wire, is caused to make and spray break contact repetitiously with successive portions of thesurface. After the desired surface area has been substantially covered by relatively.closely spaced stroke marks of fusion-deposited nickel from the nickel wire electrode, the treatment is discontinued and the surface is then sprayed in the conventional manner with bronze. Example II A source of electrical energy consisting of a direct current generator is first provided, capable of producing a voltage of 5 volts and approxi- .mately 400 amperes. One lead from the source of electric energy is connected to a bronze sleeve, the previously cleaned outside surface of which is to receive fusion-deposited metal; the other lead from the source of electrical energy is connected to a stainless steel strip of fiat wire approximately 1';" thick by A" wide. The stain less steel strip is first contacted with the surface of the bronze sleeve, preferably on the edge of the strip, and assoon as the metal of the strip electrode starts to melt thecontacted surface is lightly and intermittently stroked with the stainless steel strip over successive areas of the same whereby the end of the stainless steel strip is caused to make and break contact repetitiously with successive portions of the surface. After the desired surface of the sleeve has been substantially coveredby a large number of relatively closely spaced amounts of fusion-deposited stainless steel from the strip electrode, the treatment is discontinued and the surface is then sprayed with aluminum. Thus the article produced in accordance with he oregoing Example I constitutes a composite metal article comprising a steel base, a layer of spray bronze, and intermediate the steel base and the layer of spray bronze, nickel deposited by fusion on the steel base in interlock with the spray bronze by means of the specifically peculiar multitude of minute surface craters and overhanging characteristics of the fusion-deposited metal. The article obtained in accordance with Example H constitutes a similar composite metal article except that in this case the base is of bronze, the fusion-deposited metal, stainless steel and the therewith interlocking spray metal layer, sprayed aluminum.

When in the preparation of the products in accordance with my invention, a base of substantially cylindrical configuration is used, as,

for instance, constituted by shafts, sleeves, rods, bars and the like, it is often of advantage to apply the fusion-deposited metal by rotating the object about its axis and proceeding with the hereinabove electrode contact procedure while the object is rotating. In such case, electrode.

contact, if desired may be substantially continuous though it is preferred to usethe repetitious contact stroking method above referred to. R0-

tation of the cylindrical shaped base may be accomplished in any desired manner, it being preferred, however, to rotatably mount the same in a suitable lathe or such similar machine. Surface speed of rotation should not be appreciably inv excess of 200 feet per minute, and preferably substantially between 50 and 150 feet per minute.

When using surface speed appreciably in excess of 200 feet per minute, considerable voltage drops result by reason of reduced contact; furthermore.

' the spacing of deposited metal becomes too large and overlaps occur, thereby impairing the eiiiciency of the procedure.

The followingexample is furnished byway of illustrating a procedure of preparing a spray metal coated article in accordance with the inventio'n-having a metal surfaced base of substantially cylindrical shape and rotating the same in I a lathe:

Example III The source of electrical energy, consisting of a transformer, connected to an alternating current power supply, is first provided, capable of an average voltage between two and nine volts and approximately 400 amperes. A one-inch steel shaft of S. A. E. 1045 steel which is to be coated by metal spraying on a section of its length is mounted in a lathe, between lathe centers. One lead from the source of electrical energy is connected to the tailstock of the lathe." The other lead from the source ofelectrical energy is connected to a nickel wire of approximately $4," diameter. The shaft is rotated in the lathe at a speed of approximately 600 revolutions .per minute, and while the shaft is rotating, the nickel wire is first contacted with the surface of the shaft to be conditioned and as soon as the metal electrode starts to melt, the surface of the shaft, while still rotating, is lightly and repetitiously stroked with the nickel wire over successive areas of the same, whereby the end of the nickel wire is caused to make and break contact repetitiously with successive portions of the surface. After the desired surface area has been substantially covered by relatively closely spaced amounts of deposited nickel from the nickel wire electrode,

the treatment is discontinued and the surface is v now ready to be sprayed upon.

Within the broad scope of my invention, the

spray metal and formed by its freezing from semi-liquid state with the and projections of the type and character remultitude of craters ferred to. The applied spray metal flnnly interlocks with at least the majority of these projections and craters.

The type of' surface obtaine sition of metal on a metal sur terlock between the surface of metal and applied spray metal by the following drawings f illustration and not of limitation aiid representing reproductions of photomicrographs:

Fig, 1 illustrates a photomicrographic to view by fusion-depoace and the infusion-deposited is demonstrated of a steel base treated in accordance with the invention;

Fig. 2 illustrates a photomicrographic crosssection 'ofthe specimen shown in Fig. I; and

Fig. 3 is a photo nicrographic cross-sectional cut through a steel base treated with nickel in accordance with the invention and having a su-- perimposed spray metal coat; The deposited metal shown in the photomicrograph represented by Fig. 1 is nickel applied by the electrode contact. method on a steel base, using a nickel wire electrode. The view il1ustrated in the -photomicrograph represented by Fig. 1

is a top view, unetched, with an oblique illumination. The magnification is 50x showing the ed by way of not using too much c in the preparation of photomicrograph represented by Fig. 1 showing a view perpendicular to the prepared surface at the edge of the specimen using a conventional picral etch and 100K magnification. The overhanging projectionsand craters with overhanging edges and projections in the top layer of the electrode deposited metal are clearly shown. In the lower portion of the photomicrograph represented by Fig. 2 is the normal structure of the steel plate serving as a I base; combined by fusion to this base is the electrode deposited nickel, having the appearance of I solidified or frozen froth, foam or lava showing the projections and the many holes and pores, which at the upper surface of the nickel layer, constitute the craters with overhanging edges with which the thereafter to be applied spray metal can interlock.

The interlock between the electrod deposited metal and the applied spray metal is typified for instance by,the photomicrograph represented by Fig'. 3 which shows a cross-sectional cut through a specimen obtained by spraying steel on a sample obtained by depositing nickel on a steel base by the electrode deposition method referred to; The cut was treated in the conventional manner with a picral etch. The photomicrograph represented by Fig. 3 illustrates a 100K magnification. The lower portion of the photomicrograph represented by Fig. 3 shows the normal structure of the mild steel base used. Bonded to this by fusion is the intermediate fusion-deposited nickel layerof a characteristic frozen froth, foam 0'! lava appearance. The top surface is that of the superimposed spray steel. The characteristic craters, projections and overhanging edges of the intermediate fusion-deposited nickel layer are clearly shown in typical interlock with particles of the spray metal layer.

As afore pointed out, any commorrmetal may be used intermediate practically any base and,

any spray metaL, Thus, for instance, silver, Monel, aluminum, brass, stainless steel, inconel or the like, may be used either as fusion-deposited metal or. as base upon which the same is deposited. In most cases, however, I prefer for best results, nickel, bronze or silver as the intermediate metals and among these nickel as the most satisfactory material.

When using in the above described procedure, wire electrodes for the deposition by fusion of intermediate metal, it is of advantage to use wires, whether round or flat shaped, having a The source of electrical ing or a direct current.

If the process, herein recited by way'of example for the making of my novel spray metal coated articles, is applied using large amounts of currentsubstantially continuously on a small piece of base metal, the base may. heat up considerably. This may be controlled, however, by on small base pieces or by allowing time to elapse between the application, of the amounts ofyelectrode material to urrent the base, and also by applying cooling means, 'such as a blast of air to cool the surfaceeither maximum cross-sectional width substantially between 1%" and /4'".

energy may be one providing either an alternat- 7 consisting of spray metal.

the base surface are induced, as herein above stated, by fusion-deposition. Such fusion-deposition, within the spirit and scope of my invention, does not necessarily connote solelyfusion or deposition by fusion to the point of complete fusion of the entire deposited metal, but, also embraces deposition of metal only part of which is fused and still further includes the case in which the fusion of part or all of the deposited metal, as is well understood, does not necessarily proceed to the point of free-flowing liquidity.

In the preparation of spray metal coated articles in accordance with this invention, the spray m'etal coating is applied in any desired conventional manner. Thus the same may be applied by passing a conventional metal spray gun forth and back over the intermediate fusion deposited metal layer until a spray metal coating of the desired thickness is formed.

The foregoing specific description is for purposes of illustration and not of limitation and it is therefore myintention that the invention be limited only by the appended claims or their equivalents wherein I have endeavored to claim broadly all inherent novelty.

I claim:

1. A spray metal coated, metal-surfaced article which comprises an article having a metal surface, a layer of spray metal, and, intermediate said metal surface and said layer of spray metal, fused metal deposited upon and integrally bonded .to said surface by fusion to said sur-, face and characterized by an irregular surface frozen from semi-liquid state with a multitude of projections with over-hanging edges and minute craters with over-hanging edges, at least the majority of said projections and craters being in interlock with spray metal particles of i said layer of spray metal, and at least the ma- 2, A spray metal coated, metal-surfaced article "in accordance with claim 1 in which said intermediate metal is nickel.

' 3. A spray metal coated, metal-surfaced article in accordance with claim 1 in which said intermediate metal is bronze;

4.'A spray metal coated, metal-surfaced article in accordance with claim 1 irf which said intermediate metal is silver.

5. A spray. metal coated, metal-surfaced article which comprises an'article having a metal surface, a layer of spray metal, and, intermediate said metal surface and said layer of spray metal, fused metal deposited upon and integrally bonded to said surface by fusion to said surface and characterized by an irregular surface frozen from semi-liquid state with a multiple number of first-projections, a multitude of second projections with over-hanging edges and a multitude of rhinute craters having overhangingedges at least some of said second projections being in size and spacing substantially of the same order of magnitude as the size of spray metal particles in the spray metallayer and at least some -01 said first projections being of a higher order of magnitude, at least the majority of said secand projections and the majority of said craters being in interlock with spray metal particles of said layer of, spray metal.

6. A spray metal coated, metal-surfaced article in accordance with claim 5 in which said intermediate metal is nickel.

7. A spray metal coated, metal-surfaced article in accordance with claim 5 in; which said intermediate metal is bronze.

8. A spray metal coated, metal-surfaced article in accordance with claim 5 in which said intermediate metal is silver.

JOHN FRANK MEDUNA. 

